https://doi.org/10.7812/TPP/13-111

We would like to thank Phillip Tuso, MD, and associates for their comprehensive review of the evidence supporting the value of plant-based diets for preventing and curing the epidemic of diseases caused by overnutrition that are sickening millions of people in the US and crippling our nation's economy. However, counterproductive to the authors' goal that "physicians should consider recommending a plant-based diet to all of their patients" is the authors' dedication of a substantial portion of their article to the possibility of deficiencies of selected nutrients. In our experience of treating more than 5000 patients with a low-fat, whole foods, plant-based (vegan) diet, with follow-up lasting as long as 28 years, we have not seen any deficiencies of protein, iron, calcium, or essential fatty acids. (We do recommend to our patients a vitamin B12 supplement and adequate sunshine for vitamin D.)

Tuso et al characterize the risk of these deficiencies as low, but deserving of monitoring. The risks are so low that illnesses because of the lack of any of these essential nutrients, including protein,1 have not been reported to occur on any natural human diet (as long as calorie intake is sufficient). Dietary manipulation or supplementation to improve the overall quality, or to increase the absolute quantity, of protein, iron, calcium, or fatty acids has not been found to be beneficial. To the contrary, excess protein is a major contributor to bone loss,2 kidney stones, and kidney failure.3 Although iron stores may be lower in vegetarians, there is no reported increase in incidence of iron deficiency anemia.4 Data supporting the benefits of calcium supplementation to improve bone health is lacking, and adverse effects, such as an increased risk of fracture5 and myocardial infarction6 from supplementation have been reported.Plasma levels of essential fatty acids can be lower in vegetarians, but there has been no reported clinical consequence of this laboratory finding.7 In addition, randomized placebo controlled trials for the primary8 and secondary9 prevention of cardiovascular disease with omega-3 supplements have been disappointing as of late. Furthermore, there is concern that these "good fats" may increase the risk of common cancers, including prostate cancer.10

More than a half-century of creative marketing by the meat, dairy, egg, and fish industries has produced fears surrounding nonexistent deficiencies, which in clinical practice need no patient monitoring by physicians and dietitians. Hopefully our concerns for overemphasizing the importance of largely theoretical risk will remove an unnecessary hindrance to the acceptance and practice of scientifically sound plant-based diets as recommended by Tuso and associates.

Craig McDougall, MD

Northwest Permanente, Portland, OR

John McDougall, MD

The McDougall Program, Santa Rosa, CA

References

1. Millward DJ. Meat or wheat for the next millennium? Plenary lecture. The nutritional value of plant-based diets in relation to human amino acid and protein requirements. Proceedings of the Nutrition Society 1999 May;58(2):249-60. DOI: https://doi.org/10.1017/S0029665199000348

Response to Drs Craig and John McDougall

We thank Drs John and Craig McDougall for their interest in our article. Although we understand their point of view, from a clinical perspective, we are obligated to inform physicians of potential concerns, even if the risk for harm is low.

It may be true that eating a healthy, plant-based diet can offer the optimal amount of most nutrients needed to support health. Not every person however, will follow a quality diet, so it is important for physicians to understand what these potential concerns might be.